Possible Clues:

• Some nos. on maps
• Some numbered rds.
• Ways to go?: Abbr.
• Direction givers' suggestions: Abbr.
• Itinerary abbrs.
• I-80 et al.
• U.S. hwys., e.g.
• St. and ave.
• Carriers' paths: Abbr.
• Many begin with I: Abbr.